An example method for treating a blood vessel may include disposing a medical device within the blood vessel at a position adjacent to a lesion. The medical device may include an elongate shaft having a distal end region, a balloon coupled to the distal end region, and an iron-containing fluid disposed within the balloon. The method may also include inflating the balloon to a first pressure, delivering a plurality of electromagnetic pulses to the iron-containing fluid, and inflating the balloon to a second pressure greater than the first pressure.